This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for DOUBLE FREQUENCY HOPPING COMMUNICATION SYSTEM AND CONTROL METHOD THEREOF earlier filed in the Korean Industrial Property Office on the 23rd of June 1999 and there duly assigned Ser. No. 23731/1999.
1. Technical Field
The present invention relates to a communication device, and more particularly, to a frequency hopping (FH) communication device for frequency hopping data to be transmitted and transmitting the data to be transmitted and a method therefor.
2. Related Art
In the sciences related to communication methods, spread-spectrum modulation is a modulation technique where the bandwidth of a modulated signal is spread far beyond the bandwidth of the modulating signal, independently of the modulating signal bandwidth. Spread-spectrum modulation is sometimes used as a method to reduce the effects of intentional jamming by another source.
One technique of implementing spread-spectrum modulation is known as frequency hopping (FH). The frequency hopping technique can involve a modulated signal being hopped in a pseudorandom manner among a set of frequencies. Frequency hopping can sometimes prevent an individual from knowing which band to jam.
I have found that performance of frequency hopping devices and methods can be less than satisfactory. Efforts have been made to improve communication devices and methods.
Exemplars of recent efforts in the art include U.S. Pat. No. 5,166,953 for a technique for Frequency-hopped Spread Spectrum Communications issued to Hershey et al., U.S. Pat. No. 4,914,699 for High Frequency Anti-jam Communication System Terminal issued to Dunn et al., U.S. Pat. No.5,471,464 for Orthogonal Frequency Division Multiplex Demodulation Apparatus issued to Ikeda, U.S. Pat. No. 5,867,478 for Synchronous Coherent Orthogonal Frequency Division Multiplexing System, Method, Software And Device issued to Baum et al., U.S. Pat. No.5,793,795 for Method For Correcting Errors From A Jamming Signal In A Frequency Hopped Spread Spectrum Communication System issued to Li, and U.S. Pat. No. 5,259,030 for Antijam Improvement Method And Apparatus issued to Francis.
While these recent efforts provide advantages, I note that they fail to adequately provide an improved frequency hopping communication device and method.
To solve the above problems and others, it is an object of the present invention to provide a frequency hopping (FH) communication device which is effected less by jamming.
It is a further object of the present invention to provide a frequency hopping method performed by the frequency hopping communication device.
Accordingly, to achieve the first object, there is provided a frequency hopping communication device, comprising a first frequency hopping unit for receiving data to be transmitted, orthogonal frequency division multiplexing (OFDM) modulating the received data using the frequency of a subcarrier corresponding to a first frequency hopping code among the frequencies of a predetermined number of subcarriers, and outputting first frequency hopped data on which the data to be transmitted is loaded and a second frequency hopping unit for second frequency hopping the first frequency hopped data by mixing the first frequency hopped data with a carrier composed according to a second frequency hopping code.
The first frequency hopping unit preferably comprises a first frequency hopping code generator for generating a predetermined first frequency hopping code according to specified regulations when data to be transmitted is input to the first frequency hopping unit, a first frequency hopping data storage unit for outputting data corresponding to the first frequency hopping code as first frequency hopped data, and an orthogonal frequency division multiplexing (OFDM) modulator for orthogonal-frequency-division-multiplexing modulating the first frequency hopped data using the frequency of a predetermined subcarrier and outputting the modulated data. The frequency hopping communication device preferably further comprises a guard interval inserting unit for receiving data output from the orthogonal-frequency-division-multiplexing modulator and inserting into the data a guard interval for reducing the influence of intersymbol interference (ISI) and interframe interference (IFI) between the subcarriers.
The frequency hopping communication device preferably further comprises a digital-to-analog converter for converting data output from the guard interval inserting unit into analog data and outputting the converted analog data.
The second frequency hopping unit preferably comprises a second frequency hopping code generator for generating a predetermined second frequency hopping code according to specified regulations when analog data is input to the second frequency hopping unit and a second frequency hopping data generator for composing subcarrier data of a frequency corresponding to the second frequency hopping code, mixing the composed data with the analog data output from the digital-to-analog converter, and generating second frequency hopping data.
The predetermined first frequency hopping code preferably comprises frequency information for orthogonal-frequency-division-multiplexing modulating data to be transmitted using N predetermined subcarriers, where N is a predetermined positive number.
Alternatively, the first frequency hopping unit preferably comprises a first frequency hopping data storage unit for outputting data corresponding to the first frequency hopping code as first frequency hopped data, a serial-to-parallel converter for parallel converting the first frequency hopped data into a predetermined number of data items and outputting the parallel converted data, an N-point complex inverse-fast-Fourier-transform (IFFT) converter for N-point complex inverse-fast-Fourier-transform converting parallel converted data dp(t) using the frequencies of N predetermined subcarriers, orthogonal-frequency-division-multiplexing modulating the parallel converted data dp(t), and outputting N modulated subcarriers di(n) on which parallel converted data dp(t) are loaded, and a parallel-to-serial converter for receiving the N subcarrier data output from the N-point complex inverse-fast-Fourier-transform converter, serially converting the received data, and outputting the converted data.
The frequencies of the N predetermined subcarriers are preferably determined to be different from each other according to the first frequency hopping code used by the first frequencyhopping unit.
The N-point complex inverse-fast-Fourier-transform converter preferably outputs data di(n) by N-point complex inverse-fast-Fourier-transform converting data to be transmitted according to                     d        i            ⁢              xe2x80x83            ⁢              (        n        )              =                  1        N            ⁢              xe2x80x83            ⁢                        ∑                      k            =            0                                N            -            1                          ⁢                  xe2x80x83                ⁢                              d            p                    ⁢                      xe2x80x83                    ⁢                      (            t            )                    ⁢                      xe2x80x83                    ⁢                      ⅇ                          j              ⁢                              xe2x80x83                            ⁢              2              ⁢                              xe2x80x83                            ⁢              π              ⁢                              xe2x80x83                            ⁢                              nk                /                N                                                          ,
wherein n=1, 2, 3, . . . , and N is a predetermined positive number.
The phases of the N subcarriers are preferably orthogonal to each other. The first frequency hopping code generator preferably comprises a pseudo noise (PN) code generator for generating a pseudo noise code, an address generator for generating an address corresponding to the pseudo noise code output from the pseudo noise code generator, and a memory for outputting a first frequency hopping code corresponding to the address when the data to be transmitted is input.
To achieve the second object, there is provided a method for frequency hopping data to be transmitted and transmitting and receiving the data, comprising the steps of (a) orthogonal-frequency-division-multiplexing modulating received data to be transmitted using the frequency of a subcarrier corresponding to a predetermined first frequency hopping code among the frequencies of a predetermined number of subcarriers and outputting a first frequency hopped data on which data to be transmitted is loaded and (b) second frequency hopping the first frequency hopped data by mixing the first frequency hopped data with a subcarrier composed according to a second frequency hopping code.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a communication apparatus, comprising: a first unit receiving first data, generating a first frequency hopping code, generating first frequency hopped data in dependence upon said first frequency hopping code, modulating said first frequency hopped data, outputting said modulated data, said modulating corresponding to orthogonal frequency division multiplexing modulating, said modulated data corresponding to said received first data loaded on said first frequency hopped data; and a second unit receiving input data corresponding to said modulated data, generating a second frequency hopping code, composing carrier data in dependence upon said second frequency hopping code, mixing said composed data with said input data, and outputting second frequency hopped data corresponding to said mixing of said composed data with said input data, said received first data corresponding to data to be transmitted.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a frequency hopping communication apparatus, comprising: a first unit receiving first data, generating a predetermined first frequency hopping code, generating first frequency hopped data in dependence upon said first frequency hopping code, modulating said first frequency hopped data, outputting said modulated data, said modulated data corresponding to said received first data loaded on said first frequency hopped data; and a second unit receiving input data corresponding to said modulated data, generating a predetermined second frequency hopping code, composing carrier data in dependence upon said second frequency hopping code, mixing said composed data with said input data, and outputting second frequency hopped data corresponding to said mixing of said composed data with said input data, said first data received by said first unit corresponding to data to be transmitted.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a method, comprising: modulating first data using a frequency of a subcarrier corresponding to a predetermined first frequency hopping code, said frequency being selected from among a plurality of frequencies of a predetermined number of subcarriers, said first data corresponding to data to be transmitted; outputting first frequency hopped data on which said first data is loaded, said first frequency hopped data on which said first data is loaded corresponding to modulated data; and second frequency hopping said first frequency hopped data by mixing said first frequency hopped data with a subcarrier composed in dependence upon a second frequency hopping code.